Fibre channel arbitrated loop bufferless switch circuitry to increase bandwidth without significant increase in cost

• US 7,366,190 B2
• Filed: 01/21/2003
• Issued: 04/29/2008
• Est. Priority Date: 11/19/1998
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Black, Alistair D., Chan, Kurt
• Primary Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US10/348,642
• Publication Number:
  US 20030174721A1
• Time in Patent Office: 1,925 Days
• Field of Search: None
• US Class Current: 370/406
• CPC Class Codes: H04J 3/245 in which the allocation protocols between more than two stations share the same transmission medium stations for satellite systems H04B7/185
• CPC Class Codes: H04L 49/101 using crossbar or matrix
• CPC Class Codes: H04L 49/357 Fibre channel switches

Abstract

A switch, switched architecture and process for transferring data through an FCAL switch is disclosed. The switch uses multiple switch control circuits each coupled to one FCAL network and all connected to a crossbar switch. The switch control circuits are coupled together by a protocol bus for coordination purposes. Local conversations can occur on each FCAL loop and crossing conversations through the switch can occur concurrently. The OPN primitive is used to establish the connection before any data is transferred thereby eliminating the need for buffer memory in the switch control circuits. The destination address of each OPN is used to address a lookup table in each switch control circuit to determine if the destination node is local. If not, the destination is looked up and a connection request made on the protocol bus. If the remote port is not busy, it sends a reply which. causes both ports to establish a data path through the backplane crossbar switch.

Claims

1. A process for insuring fairness in an switch having a plurality of switch ports, each coupled to a fibre channel arbitrated loop (FCAL) net having one or more nodes coupled thereto, comprising:

assigning each switch port a priority level for use in arbitration between conflicting connect requests from multiple switch ports to an identified destination port;

circulating a fairness token among said switch ports so that each switch port receives said fairness token, holds it for a time and then forwards it to another switch port;

assigning a switch port that has said fairness token in its possession a highest one of said assigned priority levels; and

denying access to a switch port of the plurality of switch ports that possesses the fairness token until local requests for the port can be serviced.

3. The process of claim 1 further comprising:

providing a token position counter that identifies a port that holds the token; and

incrementing the token position counter in a predetermined interval of time.

4. The process of claim 3, wherein the predetermined interval of time is based on a token length register.

2. A process for insuring fairness is achieved in an switch having a plurality of switch ports, each coupled to a an fibre channel arbitrated loop (FCAL) net having one or more nodes coupled thereto, comprising:

assigning each switch port a priority level for use in arbitration between conflicting connect requests from multiple switch ports to an identified destination port;

circulating a fairness token among said switch ports so that each switch port receives said fairness token, holds it for a time and then forwards it to another switch port;

assigning a switch port that has said fairness token in its possession a highest one of said assigned priority levels;

keeping a camp list for busy ports which have received multiple connect requests from different switch ports;

when a switch port in possession of said fairness token makes a connect request to a switch port with a camp list which is not full, adding the ID of said switch port having said fairness token to said camp list;

when access to said switch port with the camp list is granted to the switch port in possession of the fairness token, forwarding said fairness token to another switch port.

5. An apparatus for insuring fairness in a switch having a plurality of switch ports, each coupled to a fibre channel arbitrated loop (FCAL) net having one or more nodes coupled thereto, the apparatus comprising:

a circulating unit configured to circulate a token between the plurality of switch ports; and

a token position counter configured to identify which of the plurality of switch ports holds the token, wherein requests of a port of the plurality of switch ports that holds the token have highest priority, and

wherein the token position counter is incremented at a predetermined interval of time,

wherein access is denied to a switch port of the plurality of switch ports that possess the fairness token until local requests for the port can be serviced.

6. An apparatus to implement a process for insuring fairness in a switch having a plurality of switch ports, the apparatus comprising:

assignment means for assigning each switch port a priority level for use in arbitration between conflicting connect requests from multiple switch ports to an identified destination port;

circulating means for circulating a fairness token among said switch ports so that each switch port receives said fairness token, holds it for a time and then forwards it to another switch port;

wherein the assigning means further assigns a switch port that has said fairness token in its possession a highest one of said assigned priority levels,

wherein each switch port is coupled to a fibre channel arbitrated loop (FCAL) net having one or more nodes coupled thereto, and

wherein access is denied to a switch port of the plurality of switch ports that possess the fairness token until local requests for the port can be serviced.

7. A computer-readable medium, encoded with computer code for causing a computer to execute a process to insure fairness in an switch having a plurality of switch ports, the process comprising:

assigning each switch port a priority level for use in arbitration between conflicting connect requests from multiple switch ports to an identified destination port;

circulating a fairness token among said switch ports so that each switch port receives said fairness token, holds it for a time and then forwards it to another switch port;

assigning a switch port that has said fairness token in its possession a highest one of said assigned priority levels; and

denying access to a switch port of the plurality of switch ports that possesses the fairness token until local requests for the port can be serviced,

wherein each switch port is coupled to a fibre channel arbitrated loop (FCAL) net having one or more nodes coupled thereto.

8. The computer readable medium of claim 7, wherein the process further comprises:

keeping a camp list for busy ports which have received multiple connect requests from different switch ports;

when a switch port in possession of said fairness token makes a connect request to a switch port with a camp list which is not full, adding the ID of said switch port having said fairness token to said camp list;

when access to said switch port with the camp list is granted to the switch port in possession of the fairness token, forwarding said fairness token to another switch port.